10 October 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera
(MOC) image shows a suite of dunes in one of the several north polar dune
fields. The bright surfaces adjacent to some of the dunes are patches of
frost. These dunes spend much of the autumn, winter, and spring seasons
covered with carbon dioxide frost. Only in late spring and in summer are
the dark windblown sands fully exposed.
Over the course of the 9+ years of the MGS mission, the MOC team has
sought evidence that sand dunes may be migrating downwind over time.
However, no clear examples of the movement of a whole dune have been
identified. On Earth, such movement is typically detectable in air photos
of the smallest active dunes over periods of a few years. Owing to the
fact that the north polar dunes spend much of each martian year under a
cover of frost, perhaps these move much more slowly than their frost-free,
terrestrial counterparts. The sand may also be somewhat cemented by ice or
minerals, likewise preventing vigorous dune migration in the present
environment.
This view covers an area approximately 3 km (1.9 mi) wide and is
illuminated by sunlight from the lower left. The dunes are located near
79.8°N, 127.1°W, and the picture was acquired on 11 September 2006.